class Person:
    def __init__(self ,name):
        self.name = name 
        self._age = 1
    def set_age(self,new_age):
        if 0 <new_age <= 120 :
            self._age = new_age
    def get_age(self):
        return self._age

person = Person("小密")
person.set_age(20)
print(f"年龄为{person.get_age()}岁")